Re: [PATCH RFC 00/10] qemu: Enable SCHED_CORE for domains and helper processes

On Thu, 2022-05-26 at 14:01 +0200, Dario Faggioli wrote: > Thoughts? > Oh, and there are even a couple of other (potential) use case, for having an (even more!) fine grained control of core-scheduling. So, right now, giving a virtual topology to a VM, pretty much only makes sense if the VM has its vcpus pinned. Well, actually, there's something that we can do even if that is not the case, especially if we define at least *some* constraints on where the vcpus can run, even if we don't have strict and static 1-to-1 pinning... But for sure we shouldn't define an SMT topology, if we don't have that (i.e., if we don't have strict and static 1-to-1 pinning). And yet, the vcpus will run on cores and threads! Now, if we implement per-vcpu core-scheduling (which means being able to put not necessarily whole VMs, but single vcpus [although, of the same VM], in trusted groups), then we can: - put vcpu0 and vcpu1 of VM1 in a group - put vcpu2 and vcpu3 of VM1 in a(nother!) group - define, in the virtual topology of VM1, vcpu0 and vcpu1 as SMT-threads of the same core - define, in the virtual topology of VM1, vcpu2 and vcpu3 as SMT-threads of the same core